The present invention relates to a valve spring retainer assembly of the type utilized in conjunction with poppet valves in internal combustion engines.
In prior art poppet valve assemblies, the valve stem is provided with one or more peripheral grooves near the tip end for receiving a valve keeper or key. Typically the key consists of a pair of mating semi-circular segments having frusto-conical outer faces and cylindrical inner faces provided with ribs for mating with the peripheral grooves in the tip end of the valve stem. The cylindrical inner faces surround the valve stem and the ribs engage the grooves in the valve stem. The conical outer face of the key provides a wedge fit with the valve spring retainer. The valve spring retainer typically has a tapered bore for mating with the frusto-conical outer surface of the key and has at least one thrust surface against which the valve spring urges the retainer upwardly against the key.
This valve spring assembly has proven to be less than adequate for high performance engines. The extreme forces exerted by the valve spring(s) on the retainer at high engine speeds often causes the keeper or key to be extruded through the valve spring retainer. The extrusion process often results in cracking and subsequently catastrophic failure of the retainer. In order to solve this problem, a flange portion has been formed integrally with the valve keeper or key, such as, disclosed in Surovek U.S. Pat. No. 3,289,658 and Tanahashi U.S. Pat. No. 4,058,091. However, as taught in the Surovek patent, the radial flange at the top portion of the split keeper directly overlies the top surface of the spring retainer such that the valve spring urges the retainer directly against the radial flange portion of the keeper. This radial flange portion has in the past been relatively thin and because of the stress concentration established where the radial flange meets the body of the keeper, such a valve retainer assembly is subject to failure at high engine operating speeds.
Others have attempted to solve the problem by forming elaborate surface geometrics between the mating surface of the keeper and the spring retainer. Thus, Newton U.S. Pat. No. Re. 24,928 discloses a value retainer assembly wherein the retainer and keeper each have a series of mating ribs and grooves for locking the retainer with respect to the keeper. More recently, Speckhart disclosed in U.S. Pat. No. 4,201,162, a smoothly tapered surface of revolution for the keeper and retainer. This of course requires close manufacturing tolerances and results in a tendency for stress concentration to occur toward the top of the keeper-retainer interface.
It therefore is an object of the present invention to provide an improved valve spring retainer assembly for use in internal combustion engines.